Sexton said in the memo that no one was injured when Sandy crashed through on Monday evening, and the campus only sustained minor damage. But power outages, which have affected most of Manhattan south of 39th Street since Monday night, continue to present “significant challenges.”

Generators were powering facilities to provide students with food and shelter Tuesday night, but the absence of Con Edison power made it extremely difficult to power classroom buildings at the same time.

“The NYU’s Deans and Directors and I met today, and based upon the best information we have available, we have decided that the most prudent course of action is to announce now that we will cancel classes for Thursday, Friday and Saturday,” Sexton wrote.

The Weinstein Residence Hall and Kimmel Center remained open Tuesday night to provide food service to all students. Plans were also in progress to shelter students safely as long as power remains out.

So that students and parents can remain in touch, locations have been set up where students can bring their phone chargers and take turns re-powering the electronic devices. The locations are at the Kimmel Center, the Global Center for Academic and Spiritual Life, and the lower level of Bobst Library.

Classes at the Mailman School of Public Health and Medical Center, and grad programs at the schools of Continuing Education and of Arts on the Morningside will not be held. The Lamont-Doherty Earth Observatory will also remain closed.

Undergraduate School of the Arts classes will meet.

“We know that transportation within the five boroughs and wider metropolitan area will remain a challenge for several days to come and that there will inevitably be some students, faculty and staff who may have special difficulty reaching our campuses,” Columbia said on its Web site. “We want to emphasize that everyone whose families, homes and neighborhoods have been severely affected by the storm have our full support in attending to their needs on the home front in the days ahead.”